<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>

  <body>
    <div id="app">
      <div>
        <p>请选择你要购买的书籍</p>
        <ul v-for="(item,index) in arr" :key="index">
          <li>{{ item.name }} <button @click="buy(index)">买书</button></li>
        </ul>
        <table border="1" width="500" cellspacing="0">
          <tr>
            <th>序号</th>
            <th>书名</th>
            <th>单价</th>
            <th>数量</th>
            <th>合计</th>
          </tr>
          <tr v-for="(item,index) in arr" :key="index">
            <th>{{ index+1 }}</th>
            <th>{{ item.name }}</th>
            <th>{{ item.price }}</th>
            <th>{{ item.count }}</th>
            <th>{{ item.price*item.count }}</th>
          </tr>
        </table>
        <p>总价格为:{{ total }}</p>
      </div>
    </div>
    <script src="../vue.js"></script>
    <script>
      const app = new Vue({
        el: "#app",
        data: {
          arr: [
            {
              name: "水浒传",
              price: 107,
              count: 0,
            },
            {
              name: "西游记",
              price: 192,
              count: 0,
            },
            {
              name: "三国演义",
              price: 219,
              count: 0,
            },
            {
              name: "红楼梦",
              price: 178,
              count: 0,
            },
          ],
        },
        methods: {
          buy(index) {
            this.arr[index].count++;
          },
        },
        computed: {
          total() {
            if (
              this.arr.reduce((pre, cur) => pre + cur.price * cur.count, 0) == 0
            ) {
              return 0;
            }
            return this.arr.reduce(
              (pre, cur) => pre + cur.price * cur.count,
              0
            );
          },
        },
      });
    </script>
  </body>
</html>
